Process for the production of moistness-resisting papers



Patented FFECE;

nnus'r runs, or HANAU, GERMANY.

PROCESSFOR THE PRODUCTION OF IVIOISTNESS-RESISTING PAPERS.

No Drawing. Application filed .October 21, 1922, Serial No. 596,140, and in Yugoslavia October 29, 1921.

By a former patent of the applicant (U. S. Patent No. 1,033,757) a process for the production of parchment paper and of papers of more or less pronounced parchment-like character and possessing varying water resistance has been protected, which consists 1n drying papers from pulps of different composition, indiiferently whether sized or unsized, at dried state or at moist state, with substances having acidic properties with or without addition of formaldehyde and at temperatures of approximately This known process is, according to the specification of the patent, carried out for instance in such a manner that finished dry parchment substitute paper is impregnated with a mixture of an approximately 6% solution of aluminium sulphate and of a 0.6% solution of formaldehyde, whereupon the impregnated paper is dried upon drying cylinders in the mannerwell known from the paper manufactory.

This process which was terminated by d the drying of the paper has however not been adopted by the manufacturers notwithstanding continuous endeavours for years, as it is impossible to produce in this manner papers possessing uniformly good properties. The main inconvenience of-the process is that the papers made according to the same became more or less brittle. A specially disagreeable circumstance is that this alteration of the resisting properties of the papers could not be perceived at once and appeared often only much later. increasing with papers which had been stored for some time in such a manner that the papers became absolutely brittle and quite unfit for use.

It has been found that it is ofessential importance not to terminate the process with the drying but to continue the treatment after the drying process proper by a subsequent heating of more or less long duration preferably at temperatures of below 100 (1, for instance at temperatures of 85- Very high, at least 100 C. or more. The working at such high temperatures is, as

quently heated whether the drying has beendone at higher temperatures, for instance of 100, or at lower temperatures, for instance 85 and The duration of the subsequent heating which depends on the quality and on the of the paper, can vary within very wide limits. ltcan be many hours but under certain conditions 'a short subsequent heating of for instance hours, 4 hours duration can give good results.

lt has further been ascertained that the quantity 'of the substances having acidic properties to be incorporated in the paper is very important for the density properties of the paper after the termination of the rying. 7,

According to the process described in my prior patent, a 6% solution of aluminium sulphate for instance is used for the im- In' a 50% impregnation of the paper. pregnation with a solution 3% of aluminum sulphate would be present in the dry paper. As has been found it is advisable to considerably reduce the quantity of the substances having acidic )roperties to be incorporated in the paper. f aluminium sulphate i'sused for. instance excellent results can be obtained with quantities of 0.5% and less remaining in the paper. In no case has it been necessary to incorporate in the paper more aluminium sulphate than 1% of the weight of the dry paper.

By the reduction of the quantity of sub stances having acidic properties incorporated in the paper in combination with the above suggested heating, at temperatures below 100 C. and of long duration, the danger of the paper becoming brittle has been absolutely avoided, all the other good properties of the paper, especially its excellent resistance to moistness being however preserved.

of this strength,

preliminary treatment Furthermore reduction of the quantity of i the substances having acidic properties per- Paper impregnated into which for instance only 0.5% or less of aluminium sulphate has been incorporated can therefore be dried in the manner described in my prior patent upon drying cylinders at temperatures of approximately 100 (1, but if in such a case at the termination of the drying process complete resistance of the paper against moistness is not obtained, the drying process must be completed by a subsequent drying period for instance in such a manner that the paper coming from the machine is subsequently heated for a longer or shorter period in a drying chamber which can be heated for instance to,temperatures between 60 and The duration of this subsequent heating depends, as has been stated above. on the one hand on the kind of paper and on the other hand on the degree of impregnation, on the composition of the im pregnating solution and the like.

The percentage in formaldehyde of the solution employed was approximately 6% according to my prior patent. It seemed to be necessary to employ such small quantities of formaldehyde since if greater quantities were used a large part of the aldehyde would probably separate from the paper, this paper acquiring as a result the disagreeable pungent smell of this substance.

Recent experiments have however led to the surprising result, that the formaldehyde is fixed in the paper by the action of the substances having acidic properties and a small quantity of the acidic substances being sufiicient to bind comparatively large quan tities of formaldehyde. Based upon this recent knowledge considerable quantities of formaldehyde, for instance up to- 4 and more per cent, can be incorporated in the paper which thus acquires excellent antiseptic and disinfecting properties.

Besides formaldehyde or formaldehyde supplying substances, other substances which possess a disinfecting action, such as benzoic acid or salicylic acid can be incorporated in the paper.

It has further been proved to be advisable to work with concentrated solutions at a very low degree of impregnation. The advantage is thus obtained that the duration of the drying can be considerably shortened and that the loss of volatile substances during the drying process, especially of the valuable formaldehyde, is thus restricted to the minimum. Excellent results can be obtained for instance with degrees of impregnation of 10% and less. lVith an 8% impregnation of the paper a solution of thirty percent formaldehyde can be usedfor instance in which is dissolved the aluminium sulphate that has to be incorporated in the paper.

Further experiments have shown that the carrying out of the process is not limited to substancessuch as supersalts or acids, but

that a number of salts, especially of chlorides can be used with advantage wh'ich, as for instance calcium chloride and magnesium chloride, possess per se neutral character and have the property to act acid-like under the given conditions. Therefore, in the claims wherever the term substances having acidic properties is used it is intended to cover not only acids and acid salts but also compounds, such as calcium chloride and magnesium chloride that have the property of acting in the manner of an acid under the particular conditions of the process constituting the present invention. I

It has further been found that the properties of the papers to be produced can be improved by the additional use of colloid bodies such as casein, animal glue and the like, which under the given conditions become hard and insoluble. The incorporation of the colloid bodies can precede the treatment of the paper with acid substances and formaldehyde, for instance by addition of casein or animal glue to the pulp. It is however possible also to add these colloid bodies in such a manner that papers which have absorbing capability are impregnated with a solution which contains for instance animal glue besides the acid substances and formaldehyde. For this working method the use of the abovementioned salts, a magnesium chloride and calcium chloride has proved to be advisable as the solutions of these salts are. capable. even in the presence of formaldehyde, of dissolving comparatively great quantities of animal glue.

Various properties can be given to the moistness-resisting paper by convenient treatment, for instance the property of suppleness by treatment with certain hygroscopic substances. lVith this object in view the special treatment of the paper with such substances is not absolutely necessary if the substances in question, for instance glycerinc. sugar and the like,are added to the moistness resisting solution. dering the paper resistant to moistness which beside the acid action are at the same time hygroscopic, the addition of special hygroscopically acting substances can be omitted.

Finally I have found that it is possible to use the process for making the paper impermeable at the same time, for colouring the paper by incorporating in the solution for making the paper moist proof pigments designed to produce the desired colouring.

It is evident thatseveral of the above mentioned substances, for instance substances designed to increase the impermeability, substances for increasing the suppleness of the paper and colouring matter can be applied simultaneously.

For impregnating the paper any of the well known moist-devices and eventually several of the same together, can be used.

If salts are used for renllti ' sprinkled l nder certain dering impermeable of meaeee Instead of using one single impregnating solution the constituents of the solution could be applied separately, one surface of the paper sheet could for instance be painted with a concentrated mixture of dissolvents and a diluting substance for instance could be used for painting the other surface. conditions the impregnating with heated solutions or mixtures of solutions has proved to be advantageous.

The working method composed of three operations: impregnation, drying and subsequent heating, can be considerably simplilied by executing the impregnation directly -with the drying process for instance in using an impregnating press in such a manner that the paper is conducted through a heat- :ihle dipping device whereupon it is immediately submitted to pressure and conducted over the drying cylinders. \Vith this working method also the constituents of the impregnating liquid can be applied separately for instance in such a manner thatthe paper is first impregnated with hot salt solution, and pressed whereupon shortly before it gets upon the drying cylinder, formaldehyde is applied to the paper, for instance by sprinding, by conducting the paper over *ollers with formaldehyde or in any other convenient manner, the formaldehyde being preferably applied uponthe surface of the paper which comes in contact with the drying cylinder, wherefrom results, that the formaldehyde, evaporated by the heat, is driven by diffusion at a uniformly distributed state into the paper sheet. The Working with impregnating presses has proved to be advantageous in cases in which the renthe paper has been combined with the colouring of the same.

The process is adopted, amongst other uses, also for the rendering moist proof of spun papers designed to be used for the'production of paper threads, paper fabrics or the like. Spun paper rendered moist proof according to this process can be worked directly into impermeable paper threads, fabrics or the like. It is however advisable to insert the impermeating css for manufacturing the paper thread. This can be done in such a manner that for instance the paper in strips, which is spun to threads by simple twisting Whilst being moistened, is impregnated instead. of with water with a solution which according to the invention is designed for rendering the paper moist proof, the paper threads being then dried. and subsequently heated.

The impermeable paper produced according to the invention can further be refined and improved by being heated in a known manner with varnish, asphaltum, pitch. tar or the like. In the coatings thus applied, threads, light fabrics or the like could be embedded.

process in the procproperties,

'num sulphate and with 'tures below 100 C.

By gluing together several moist-proof paper sheets impermeable cardboard can be made. By gluing together impermeable paper sheets and paper sheets which are not impermeable products can be made which are impermeable upon one surface only. F or the gluing any convenient glue can'be used. Paper sheets covered with asphaltum, pitch and the like can be made into cardboard without the use of special glues. The gluing together of several paper sheets can preferably be made in one operation with the impermeating for instance in such a manner that the agglutinant is applied between the paper sheets to be united by pressure, of which at least one is impregnated with the solution designed to render the same moist-proof, whereupon the drying is effected.

I claim 1. The herein described process for the production of moistness resisting paper consisting in impregnating the paper with a solution having acidic properties, in drying the impregnated paper at temperatures below 100 C. and in submitting the dried paper to a subsequent heating at temperatures-from about C. to about 100 C.

2. A. process for the production of moistness resisting paper consisting in impregnating the paper with solutions having acidic properties, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried'paper to a subsequent heating at temperatures from about 60 C. to about 100 C. j

3. A process for the production of moistness resisting paper consisting in impregnating the paper with solutions having acidic in drying the impregnated paper at ten'iperatures below 100 C. and in submitting the dried paper to a subsequentheating at temperatures to about 100 C.

4. A process for the production of moistness resisting paper consisting in impregnating the paper with a solution of aluminum suiphate as a solution having acidic properties and with formaldehyde, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures approximately between 6 0 C. and 100 C.

5. A process for the production of moistness resisting paper consisting in impregnating the paper with not more than 1% alumiformaldehyde, in drying the impregnatedpaper at temperaand in subjecting the dried paper to a subsequent heating at temperatures from about 60 C. to about 100 C;

6. A process for the production of moistness resisting ing the paper with substances having acidic properties and with more than 4% formaldefrom about 00 C.'

paper consisting in impregnat- -to render the paper supple, and with hyde, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures from about 00 C. to about 100 C.

7. A" process for the production of moistness resisting paper consisting in impregnating the paper with not more than 1% aluminum sulphate and with more than 4% formaldehyde, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures from about. 00 C. to about 100 C.

8. A' process tor the production of moistness resisting paper consisting in impregnat ing the paper with substances having acidic properties and with antiseptic substances of which one is formaldehyde, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures from about C. to about 100 0. A process for the production of moistness resisting paper consisting in iu'ipregnating the paper with substances having acidic properties and at the same time are adapted formaldehyde, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures from about 00 C. to about 100 C. I

10. A process for the production of moistness resisting paper consisting in impregnating the paper with substances having acidic properties, with antiseptic substances of which one is formaldehyde and with organic colloids, in dryingthe impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures from about (30 C. to about 100 C.

1.1. A process for the production of moistness resisting paper consisting in impregnating the. paper with substances having acidic properties and at the same time are adapted to render the paper supple, with formaldehyde, and with organic colloid substances, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures from about 00 C. to about 100 C.

12. A process for the production of moistncss resisting paper cousiiting in impregnating the paper with substances having acidic properties and which at the same time are adapted to render the paper supple, with formaldehyde, with organic colloid sub-- stances and with coloring substances, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures from about (50 C. to about 100 C.

13. A process for the production of moistness resisting paper consisting in impregnating the paper with substances having acidic. properties and with formaldehyde, in such a manner that solutions for higher concentrations are used at degrees of impregnation which amount to less than 10% ot' the weight of the paper pulp, in drying the impregnated paper at temperatures below 100 C. and in subjecting the dried paper to a subsequent heating at temperatures from about 60 C. to about 100 C.

In testimony whereof I afiix my signature.

ERNST FUES. 

